mirror of https://github.com/docker/docs.git
151 lines
5.3 KiB
Markdown
151 lines
5.3 KiB
Markdown
---
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description: Learn how to scale Docker Universal Control Plane cluster, by adding
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and removing nodes.
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keywords: UCP, cluster, scale
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title: Scale your cluster
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---
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Docker UCP is designed for scaling horizontally as your applications grow in
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size and usage. You can add or remove nodes from the UCP cluster to make it
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scale to your needs.
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Since UCP leverages the clustering functionality provided by Docker Engine,
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you use the [docker swarm join](/engine/swarm/swarm-tutorial/add-nodes.md)
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command to add more nodes to your cluster. When joining new nodes, the UCP
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services automatically start running in that node.
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When joining a node to a cluster you can specify its role: manager or worker.
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* **Manager nodes**
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Manager nodes are responsible for cluster management functionality and
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dispatching tasks to worker nodes. Having multiple manager nodes allows
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your cluster to be highly-available and tolerate node failures.
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Manager nodes also run all UCP components in a replicated way, so by adding
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additional manager nodes you're also making UCP highly available.
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[Learn more about the UCP architecture.](../../architecture.md)
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* **Worker nodes**
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Worker nodes receive and execute your services and applications. Having
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multiple worker nodes allows you to scale the computing capacity of your
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cluster.
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When deploying Docker Trusted Registry in your cluster, you deploy it to a
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worker node.
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## Join nodes to the cluster
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To join nodes to the cluster, go to the **UCP web UI**, navigate to
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the **Resources** page, and go to the **Nodes** section.
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{: .with-border}
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Click the **Add Node** button to add a new node.
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{: .with-border}
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Check the 'Add node as a manager' option if you want to add the node as manager.
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Also, set the 'Use a custom listen address' option to specify the IP of the
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host that you'll be joining to the cluster.
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Then you can copy the command displayed, use ssh to **log into the host** that
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you want to join to the cluster, and **run the command** on that host.
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{: .with-border}
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After you run the join command in the node, the node starts being displayed
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in UCP.
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## Remove nodes from the cluster
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1. If the target node is a manager, you will need to first demote the node into
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a worker before proceeding with the removal:
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* From the UCP web UI, navigate to the **Resources** section and then go to
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the **Nodes** page. Select the node you wish to remove and switch its role
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to **Worker**, wait until the operation is completed and confirm that the
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node is no longer a manager.
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* From the CLI, perform `docker node ls` and identify the nodeID or hostname
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of the target node. Then, run `docker node demote <nodeID or hostname>`.
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2. If the status of the worker node is `Ready`, you'll need to manually force
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the node to leave the swarm. To do this, connect to the target node through
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SSH and run `docker swarm leave --force` directly against the local docker
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engine.
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>**Warning**: Do not perform this step if the node is still a manager, as
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>that may cause loss of quorum.
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3. Now that the status of the node is reported as `Down`, you may remove the
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node:
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* From the UCP web UI, browse to the **Nodes** page, select the node and
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click on the **Remove Node** button. You will need to click on the button
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again within 5 seconds to confirm the operation.
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* From the CLI, perform `docker node rm <nodeID or hostname>`
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## Pause and drain nodes
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Once a node is part of the cluster you can change its role making a manager
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node into a worker and vice versa. You can also configure the node availability
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so that it is:
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* Active: the node can receive and execute tasks.
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* Paused: the node continues running existing tasks, but doesn't receive new ones.
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* Drained: the node won't receive new tasks. Existing tasks are stopped and
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replica tasks are launched in active nodes.
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{: .with-border}
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If you're load-balancing user requests to UCP across multiple manager nodes,
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when demoting those nodes into workers, don't forget to remove them from your
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load-balancing pool.
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## Scale your cluster from the CLI
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You can also use the command line to do all of the above operations. To get the
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join token, run the following command on a manager node:
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```none
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$ docker swarm join-token worker
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```
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If you want to add a new manager node instead of a worker node, use
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`docker swarm join-token manager` instead. If you want to use a custom listen
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address, add the `--listen-addr` arg:
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```none
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docker swarm join \
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--token SWMTKN-1-2o5ra9t7022neymg4u15f3jjfh0qh3yof817nunoioxa9i7lsp-dkmt01ebwp2m0wce1u31h6lmj \
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--listen-addr 234.234.234.234 \
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192.168.99.100:2377
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```
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Once your node is added, you can see it by running `docker node ls` on a manager:
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```none
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$ docker node ls
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```
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To change the node's availability, use:
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```
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$ docker node update --availability drain node2
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```
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You can set the availability to `active`, `pause`, or `drain`.
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To remove the node, use:
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```
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$ docker node rm <node-hostname>
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```
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## Where to go next
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* [Use your own TLS certificates](use-your-own-tls-certificates.md)
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* [Set up high availability](set-up-high-availability.md)
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